The display devices used in elevator cars and on landings and their operation are subject to many requirements. The displays must be clear and they have to be able to display sufficient information in a visually effective form. They must have a construction permitting direct installation in their physical environment without changes or at most after standard changes.
From the point of view of elevator supply logistics, it would be an advantage if a given type of display device could be used in many types of elevators and for different purposes in the same elevator system. The costs of manufacture and installation of the display device should be reasonable. However, no such display device is available.
A typical display device used in elevator cars and on landings generally indicates the position of the elevator car by means of a floor number or other sign, e.g. a letter symbol. Such a display does not indicate the state or direction of possible motion of the elevator car. However, a mere number or other symbol indicating the floor is not very informative in itself.
There are also display units that show all the stopping floors of the elevator as a series of floor symbols, one of which is highlighted at a time, e.g. by illumining the symbol, to indicate that the elevator car is at the highlighted floor. The motion and travelling direction of the car only become apparent when a new floor symbol is highlighted as the car reaches the floor corresponding to this new floor symbol. Sometimes the direction of motion may be indicated by means of a direction arrow, either a separate one or one comprised in the display. However, a direction arrow only indicates the travelling direction and does not convey an impression of the movement of the elevator. In some cases, message texts and even information about matters unrelated to the elevator system may be displayed.
U.S. Pat. No. 5,194,702 presents a display device which indicates the position of the elevator car with a stationary symbol when the elevator is standing still and in which the symbol indicating the position of the elevator car is scrolled in a vertical direction as the car moves. The symbol is scrolled upwards when the car is ascending and downwards when the car is descending. This creates a visual impression of the car movement and its direction. According to the specification, direction arrows can be displayed by the device. The device can also be used to display other messages. However, the display used in the apparatus has a small height, about equal to the height of a symbol, and is therefore insufficient in respect of visual efficiency. The position of the elevator car is not necessarily revealed to the passenger at a glance. This is the case e.g. when the elevator car is between floors and one symbol has partially moved off the display while the symbol representing the next floor is not yet completely displayed.
It can also be stated that the scrolling of character strings such as texts in a display is known in itself.